1. Field of the Invention
This invention relates generally to a stop clutch assembly, and more particularly to a stop clutch assembly for use with a power driven bi-directional rotating shaft which is subject to back loading.
2. Description of the Related Art
Power driven shafts subject to back loading are well known in the field of control systems where, for instance, a servo electric motor is utilized to position a valve in a pipeline having a fluid flowing therein. Variations in fluid flow may cause backloading of the power driven shaft, thereby altering the valve position. Since positive positioning is desirable, various methods have been utilized to prevent significant backdrive.
One such approach involves using a spring loaded brake disk adapted to co-act with a friction disk fixed to a fixed housing for the power driven shaft. The brake disk is formed as part of a power takeoff member adapted to transmit power from the shaft to a load. Spring pressure maintains the brake disk against the friction disk to prevent backloading of the shaft. Any subsequent backload is braked by this engagement. However, a disadvantage exists with the spring loaded brake disk since the spring pressure necessary to resist backloading causes excessive drag with respect to driving positioning loads.
U.S. Pat. No. 3,667,578 (xe2x80x9cthe ""578 patentxe2x80x9d) for a bi-directional drive released brake, which is incorporated herein by reference, eliminates the above identified disadvantage by providing an improved stop clutch assembly. The stop clutch assembly of the ""578 patent improves on the spring loaded brake disk of the prior art by transmitting power from the shaft to the load through a collar and ball drive which lifts the brake disk off of the friction disk upon rotation of the drive shaft. Cessation of power allows the spring pressure to force the brake disk back into braking engagement with the friction disk. The ""578 patent also discloses manual positioning of the load using a wheel located at the motor end of the drive shaft. However, in practice, manual rotation has been found to be difficult in high torque applications. Additionally, since manual rotation of the motor shaft in the stop clutch assembly of the ""578 patent occurs through the motor itself, the user may damage the internal components of the system when manually assisting the motor. Therefore, the stop clutch assembly of the ""578 patent does not provide a system which enables a user to manually position a load, while simultaneously preventing internal damage to the mechanism itself.
Accordingly, there is a need for an improved stop clutch device which enables manual high torque rotation of a load, and further provides a means for preventing damage to the stop clutch mechanism itself.
According to one aspect of the invention, a stop clutch assembly comprises a shaft for receiving a driving torque. A drive collar is concentrically fixed to the shaft. A clutch disk is rotatably disposed about the shaft and is axially slidable thereon. The clutch disk has a first surface which is adjacent to a collar surface of the drive collar. The first surface of the clutch disk and the collar surface of the drive collar each have at least one conical depression formed therein, such that each conical depression in the first surface of the clutch disk is opposingly aligned with a corresponding conical depression in the collar surface of the drive collar. A biconical clutch cavity is formed between each of the correspondingly aligned conical depressions in the collar surface of the drive collar and the first surface of the clutch disk. Each biconical clutch cavity has a clutch ball lodged therein.
A power takeoff member is rotatably disposed about the shaft. The power takeoff member is connected to a load. A takeoff surface of the power take off member is adjacent to a second surface of the clutch disk which is opposite the first surface of the clutch disk. The takeoff surface of the power takeoff member and the second surface of the clutch disk each have at least one conical depression formed therein, such that each conical depression in the second surface of the clutch disk is opposingly aligned with a corresponding conical depression in the takeoff surface of the power takeoff member. A biconical drive cavity is formed between each of the correspondingly aligned conical depressions in the takeoff surface of the power takeoff member and the second surface of the clutch disk. Each biconical drive cavity has a drive ball lodged therein.
A ring gear has a friction collar attached thereto. The ring gear is rotatably disposed about the shaft. The ring gear is positioned on the shaft such that a surface of the friction collar opposes the clutch disk. The clutch disk is engaged with the friction collar when the clutch disk is in a first position, and the clutch disk is disengaged from the friction collar when the clutch disk is in a second position.
According to a second aspect of the invention, a clutch disk is rotatably disposed about a shaft and is axially slidable thereon. The clutch disk has a first surface which is adjacent to a collar surface of a drive collar. The first surface of the clutch disk and the collar surface of the drive collar each have at least one conical depression formed therein, such that each conical depression in the first surface of the clutch disk is opposingly aligned with a corresponding conical depression in the collar surface of the drive collar. A biconical clutch cavity is formed between each of the correspondingly aligned conical depressions in the collar surface of the drive collar and the first surface of the clutch disk. Each biconical clutch cavity has a clutch ball lodged therein.
A power takeoff member is rotatably disposed about the shaft. The power takeoff member is connected to a load. A takeoff surface of the power take off member is adjacent to a second surface of the clutch disk which is opposite the first surface of the clutch disk. The takeoff surface of the power takeoff member and the second surface of the clutch disk each have at least one conical depression formed therein, such that each conical depression in the second surface of the clutch disk is opposingly aligned with a corresponding conical depression in the takeoff surface of the power takeoff member. A biconical drive cavity is formed between each of the correspondingly aligned conical depressions in the takeoff surface of the power takeoff member and the second surface of the clutch disk. Each biconical drive cavity has a drive ball lodged therein.
A ring gear has a friction collar attached thereto. The ring gear is rotatably disposed about the shaft. The ring gear is positioned on the shaft such that a surface of the friction collar opposes the clutch disk. The clutch disk is engaged with the friction collar when the clutch disk is in a first position, and the clutch disk is disengaged from the friction collar when the clutch disk is in a second position.
A drive member engages the ring gear. The drive member effects rotary motion of the ring gear when an external force is applied to the drive member. The drive member otherwise locks the ring gear.